Grainger Bioinformatics Center, Field Museum of Natural History, Chicago, IL, USA.
Jackson School of Geosciences and Integrative Biology, University of Texas at Austin, Austin, TX, USA.
Sci Adv. 2020 May 13;6(20):eaba0187. doi: 10.1126/sciadv.aba0187. eCollection 2020 May.
One of the two lineages of extant birds resulting from its deepest split, Palaeognathae, has been reported not to exhibit structural coloration in feathers, affecting inferences of ancestral coloration mechanisms in extant birds. Structural coloration in facial skin and eggshells has been shown in this lineage, but has not been reported in feathers. We present the first evidence for two distinct mechanisms of structural color in palaeognath feathers. One extinct volant clade, Lithornithidae, shows evidence of elongate melanin-containing organelles uniquely associated with glossy/iridescent color, a structural color mechanism found in fossil outgroups and neognath birds. We also demonstrate a structural basis for the exceptional gloss in extant cassowary feathers. We propose gloss as an intermediate phenotype between matte and iridescent plumage, conferred by a thick and smooth feather rachis. Rachis-based structural color has not been previously investigated. The new data illuminate the relationships between avian melanin-based coloration and feather structure.
现存鸟类的两个谱系之一，古颚总目，据报道其羽毛不具有结构色，这影响了对现存鸟类祖先颜色机制的推断。在这个谱系中已经发现了面部皮肤和蛋壳的结构色，但尚未在羽毛中报道。我们提出了古颚总目羽毛中存在两种不同结构色机制的第一个证据。一个已灭绝的飞行类群，鸵鸟目，显示出与有光泽/虹彩颜色独特相关的长黑色素包含细胞器的证据，这种结构色机制在化石外群和新颌鸟类中发现。我们还证明了现生食火鸡羽毛异常光泽的结构基础。我们提出光泽是介于哑光和虹彩羽毛之间的中间表型，由厚而光滑的羽轴赋予。羽轴结构色以前没有被研究过。新数据阐明了鸟类基于黑色素的颜色与羽毛结构之间的关系。
